UPDATE 2-Soccer-Police arrest 51 fans after Serbian derby

* Fans clash with police and set fire to stadium seats

* Partizan edge closer to title after beating Red Star

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By Zoran Milosavljevic

BELGRADE, April 8 (Reuters) - Police arrested 51 fans after crowd trouble marred a Serbian first divison derby between Partizan Belgrade and bitter rivals Red Star on Wednesday, Belgrade media said.

Beta news agency said Red Star fans set stadium seats on fire after the game and clashed with riot police before kickoff, while Serbian television showed footage of a huge blaze in the northern tier of Partizan's ground.

Fire brigades moved in and although no casulaties have been reported, the incident is likely to draw serious repercussions by the Serbian Football Federation and the authorities.

The fixture has a history of crowd trouble, dating back to times when Serbia was still a part of the former Yugoslavia.